Centrifugal dust collector



July l2, 1960 c. H. WHITMORE 2,944,632

CENTRIFUGAL DUST COLLECTOR Filed Sept. 11, 1956 3 Sheets-Sheet 1 /f/ci.

July 12, 1960 c. H. wHlTMoR'E 1 CENTRIFUGAL DUST COLLECTOR s sheets-smet 2 Filed sept. 11, 1956 July 12, 1960 l c. H. wHlTMoRE 2,944,632

CENTRIFUGAL DUST COLLECTOR Filed Sept. 11, 1956 3 Sheets-Sheet 3 A Ayn-wrok (H4/e255 HMV/*Maar United Statesl Patent O n 2,944,632 Y CENTRIFUGAL DUST COLLECTOR Charles H. Whitmore, 2517 W. 66th St., Y ,Minneapolis`, Minn. n Filed sept. 11, 1956, ser. N6. 609,299

8 Claims. (Cl. 18S-77) i This invention relates to dust collectors, and more particularly to a rotary driven dus-t collectorV of the centrifugal type. Y o

=In the art of separating suspended solid particles or dust from a gas suchv as air, many devices have been proposed. For example, the conventional dust filter separates dust from the air through'actualcollectionupon the surface of a screen or fibrous body as the air passes therethrough. The dust' filter is physically large considering the quantity of air which can pass through it per unit of time. Y the resistance of the dust filter becomesr greater and Athe power requirements also become greater, in order to force air through the even decreasing porosity of the mat. 'Ihe ordinary dust filters willnot handle hot or I n'nnidv gases, nor are they ordinarily adapted to corrosive atmospheres. The large internal volume and particularconstruction required in dust filter apparatus reduces the possibility of retaining dust explosions. In certain instances, electrical collectors or precipitators are employed, and these also are found wanting in many respects. As a rule, the electrical dust collector cannot handle a heavy concentration of'dust and the eiciency of collection varies `withrhufmidity of the gaseous medium. The cost of operation is usually quite high and there is also present the dangerV of not being able to retain dust explosions when organic nely divided material is thus precipitated.

Another type of dust collector used in the prior artis the wet scrubber. This type of dust collector is usually quite large for its collection capacity and the finelyv divided solids or dust cannot be reclaimed inv dry form since a liquid is used to collect thematerial. Where water is used in the scrubber, andthe device is subject to outside temperatures, such equipment is often in danger of damage from freezing.

We are concerned in this specification only with the As the filter mat builds up upon the surface, y y

art which relates to such separation of dust or other fine I ly divided particles suspended in a gaseous medium which can be accomplished by centrifugal action upon the particles. In a centrifugal or inertia type dust collector, there are certain'important qualities which should -be strived for. Broadly speaking, these qualities are high 1 separating efficiency, ample capacity and a low power consumption. f In order'to obtain good separating eiciency with high capacity, it is recognized that the greater the centrifugal force, the faster the particles will be separated from the gas if all .the other variables remain constant. Dust or suspended particles fall, due to the force of gravity, at diierent rates through a given gas, depending upon the density, shape and sizeof the particle. Larger particles fall at a rate which can conveniently be measured in feet per minute. Very small particles settle at a much slower rate and often` mustbe measured in inches per hour. Centrifugal force can be employed as a substitute for gravity for increasingthe rate of fall of such particles. If the centrifugal force is great enough, very small particles which may fallin time intervals measured in hours, under normal circum- Y 2,944,332q Patented July 12, 1960 ice ' through the collector faster and increase the capacity of theapparatus. Conversely, a smaller collector may be employedto achieve the same separation and capacity if a greater centrifugal force is applied. It is, of course, well 4known that the centrifugal force may be increased by increasing the radius or increasing the angular velocity of the centrifugal collector rotor. Centrifugal force Varies directly as the radius of the pathway of a given particle-.and varies -as'the squarepof the angular velocity. f In the vcase of conventional centrifugal collector design, it has often been found that the rate of speed of the rotor is. limited because of the dangerous stresses placed `upon the materialof construction. Also, where the design of the equipment is such. as4 to have stationary parts presenting pockets and sharp edges to rapidly moving parts which are in proximity thereto, a turbulence ma'y beset up which will increase with speed and oi-set the'added radvantage from higher centrifugal force. It should also be pointed out that the higher the speeds of rotation, the greater the power consumption will be. Where there is turbulence, in the area of the deposited dust, theeddy currents of air or other gaseousvmedium tends'ttopickl up dust which has already been separated, and again returns it to the gas stream. Dust particles thus returned to the main body of air or gaseous medium must be again separated and withdrawn from the ap-v paratus before the airstream is discharged or the separation will be ineicient. In some existing centrifugal collectors, a radius of as much as live feet is employed and local turbulent conditions may exist Where the dust must travel through such great distances. In order to compensate for the diiculties created by the large diametered equipment, some dust collectors have been redesigned to v employ a multiplicity of small centrifugal units. Radial distances as sm-all as one linch have been employed and turbulence may be minimized where such small radii are employed, but the increased resistance of the multiplicity of centrifugal spiralling gas streams again raises the power requirements of the apparatus. 'Such devices are relatively expensive, large in size, and generally cannot retain dust explosions. t

The collector apparatus disclosed herein and constituting my invention is provided with specially designed gas passages that greatly improve the centrifugal separating characteristics of theY dust-laden gas and keep the turbulence at a minimum while accommodating fa high capacity of gas to be centrifugally treated. By reducing turbulence in my centrifugal collector, I have been able to reduce power requirements. Additionally, I have devised yet another system for further markedly" reducing YVAnother 'object of the invention is to provide a centrifugal dust collector of improvedA characteristics which will separate a higher percentage of suspended solids of small particle size from a constantly fed flow of gas. l

A further Yobject of the invention is to provide a centrifugal dust collector in which the rotor construction minimizes turbulence and remixingof air and solids as A still further object of the invent-ion is to provide a centrifugal dust collector which will adapt itself to strong construction with a high capacity Yof air Ato be cleaned, .and will be capable of safely retaining dustexplosions without rupturing the equipment..

Yetanother object of the invention is to provide a dust collector which will have efficient separating characteristics and, at the same time, will reclaim drivingpower normally lost in the clean air discharge so as to permit a relatively lower power consumption for the capacity of the device.

Figure 1 is a vertical section taken through my 4entire centrifugal collecting device, certain portions being .shown in full line and Vportions unessential to the invention being cut away;

Figure 2 is an enlarged vertical section taken on the line 2-2 of Figure 1 adjacent the discharge Yend of the i collector;

Figure 3 is an enlarged vertical section taken on the line 3-3 of Figure 1, and showing the collecting and discharge mechanism as well as the internal construction of the rotor;

Figure 4 is an enlarged vertical section similar to Fignre 3, but showing an alternate form of rotor construction;

Figure 5 is a fragmentary view of the inlet in horizontal section taken on the line 5 5 of Figure 1;

Figure 6 is a fragmentary view of the inlet in vertical .section taken on the line 6-6 of Figure 1; and

Figure 7 is a vertical section through the outlet housing `taken on the line 7-7 of Figure 1, showing the diffuser structure.

yWith continued reference to the drawings, Figure 1 shows my assembled dust collector wherein most of the parts are symmetrically arranged so as to present a dynamically balanced device during operation. A housing is indicated generally at 10 and comprises a main rotor housing 11 which is cylindrical in shape and provided with smooth inner walls 12, as shown. One end of the cylindrical housing 11 is the intake end 13 and-the other end is the discharge or outlet end 14. The main rotor housing 11 is provided with a longitudinal discharge slot .or opening 15, as shown in Figures 1 and 3. An intake housing 16 has a peripheral iiange 17 which mates with, and is secured to, a corresponding flange 18 formed at the inlet end 13 of main rotor housing 11. Housing 16 is provided at its `bottom with a discharge slot 16a. An outlet housing 19 has a peripheral ange 20 which mates with, and is secured to, corresponding flange 21 at the outlet -end 14 of the main rotor housing 11. Supporting ,structure 22 is secured to the outlet housing 19 and a bearing member 23 is secured coaxially with the main rotor housing at the outlet end of the device. At the `inlet end of the device, a pre-swirling mechanism 24 com- .prises a shell 25 which is secured to, and communicates with, the intake housing 16 and is provided with tangential inlet 26 as shown in Figure 6. A spiral blade member 27 is iixedly secured within the pre-swirler shell 25 by such means as bolts 28, and the shell 25 is secured at its for- :ward end to inlet housing 16 by such means as bolts 29 and to supporting framework 30 by means of bolts 31, as shown in Figure 1.

A separate depending trough 32 underlies the discharge I sageway 38 which communicates in ,a short horizontal tube 39 which, in turn, communicates with a discharge spout 40. A second screw conveyor 41 is journaled across'the spout 40 and in the depending portion 37 in bearings 42 and 43, respectively. The second screw conveyor 41 in 2,944,632 v f s tube 39 creates an air choke duringl use. The screws 33 and .41 have sprockets 44 and 45, respectively, which in turn are interdriven by the roller chain 46, as shown. Motor M drives the screw conveyor 41 through coupling 47, the motor having a mount 48 secured in turn to'trough 32. The screw conveyors and their associated parts constitute the collecting and discharge mechanism indicated generally at 49.

The pre-swirler 24 is provided with a rear wall 50 upon which is secured a bearing 51. A shaft 52 extends through bearing 51 and is provided with a sheave 53 at its outer end. Sheave 53 is driven through multiple belts 54 which, in turn, are engaged with the sheave S5 secured to shaft 56 of the main motor drive 57, all as shown in Figure 1. As a part of the shaft 52, there is a flared concentric member S8 which is rigidly secured to one end of the chambered rotor element 59. Another ilared member 60 is secured to the opposite end of the rotor 59 and shaft 52 terminates in the bearing 23 secured .totheV outer end of the outlet housing 19. The chambered rotor element 59 may be hollow at its center with the inner Walls V61 defining a central space. Centrifugal action adjacent the axial line of shaft 52 does not have much practical use.

Referring now to Figure 3, the rotor 59 is provided with a'multiplicity of longitudinal and horizontal passageways `or chambers 62 which are of smooth constant .cross sec- Vtion and arranged peripherally about the inner Wall 61. Each of the-chambersl 62 narrows outwardly in a slot -63 which terminates in a peripheral outlet 64 closely adjacent the smooth inner wall surface 12 of the main rotor housing 11. A second series of horizontal passageways 65 are also arranged radially about the shaft52 `and are provided with elongated and narrow slot openings 66 which lie substantially in the same circumferential surface with the slotted openings 64. The openings 64 and 66, the passageways 63, 62 and 65 are all substantially in parallel alignment with the `shaft 52. The passageways 62 and 65 are adapted to receive dust-laden air and to discharge dust or iinely divided particles through the respective slotted openings 64 and 66 at the inner peripheral surface 12 of the main rotor housing 11. An end plate 59a is secured over the rotor 59 as shown in Figure 2. End plate 59a has lingers 59h which cover the slots 63 to prevent dust from `passing outtinto the discharge passageway 14. Plate 59a does not, however, cover the openings or passageways 62 or 65 and, hence, permits clean air to pass outwardly through discharge 14. Lugs 59C are mounted peripherally of the end plate 59a and rotate therewith to create a slight reduced pressure between the housing and rotor which amounts to an air seal.

The flared member 58 passes through a ixed spiral vane 27 in the pre-swirler 24 and rotates relatively thereto. A plurality of vanes 67 comprises a momentumconditioning element and are secured to the flared member 58in the intake housing 16. The blades 67 may have a smaller radius at the intake edge 68 than they do at the opposite edge 69. In such case, some energy must lbe added to bring the air up to its highest speed. An annular plate '711 is interposed between the connecting anges 17 and 18 so as to cause the incoming air to be guided as it leaves the momentum-conditioning blades 67 into the elongated passageways 62 and 65, and away from the space between housing 11 and rotor 59. As the rotor 59 turns, dust is centrifugally forced outwardly through the slots 64 and 66 as will be described in more detail in connection with the specific example described below.

My energy reclaiming member '71 has a plurality of blades 72 which are, in turn, radially secured to the ared member 60 Within the discharge or outlet housing 19. Each of the blades 72 has an effective diameter approximating-that of the rotor 59 at the discharge end of the device and rotates in fixed' relationwith the rotor 59 and its passageways 62 and 65. lIntermediate the inner andV outer ends of the blades 72, the effective diameter 's of the energy reclaiming member 72 may be diminished at 73 to correspond to an increase in d'iameter of blades 67 at the other end of the collector. When so diminished,

the lateral velocity of the air is, therefore, greatly increased at this point, while its rotating velocity is de- Aterminated in outlet 76 is further provided with a diffuser s 77 ywhich is ared from the outlet 76 outwardly to terminate in a dischargemouth 78. The diffuser 77"causes the air flowing through the collector to expand volumetrically as it approaches the discharge 78. Since the quantity of air does not increase in value per unit of time, the velocity must ktherefore be sharply d'ecreased as the air progresses from theY tangential outlet 76 to the discharge mouth 78. The decrease in velocity ofthe air causes a translation of kinetic energy to pressure energy and the reduced pressure at the tangential outlet 76 further. causes a partial vacuum to be pulled across the entire collector as willbe presently described. The particular design of the diffuser is not critical and may be varied to suit the individual circumstances arising in each application of my invention. For general application, I have found that a linear increase of cross sectional area resulting from an eight degree flare on all sides of the diuser 77 will usefully suit my purpose.

Referring now to Figure 4, I there show a somewhat different form of rotor which is more suitable for larger size constructions and for adapting the rotor for interchangeable chamber structure utilizing the same inner wall or core structure. '[he alternate rotor is indicated at 79 and may be housed within the same housing 10 described in connection with the lirst form. Similarly, the same collecting and discharge mechanism 49 may be employed. The inner wall or core structure 80 is mounted on axis 52 and provides the supporting struc ture for chambered members 81, as shown. Each of the chambered members 81 has an elongated plate 82 secured at its inner end 83 to the outer periphery ofthe core or inner wall 80. The plate 82, in turn, has a plurality of webs 84, 85 and 86, secured thereto at their inner edges and in spaced relation, as shown. The outermost edge of plate 82 may be bent laterally at 87. The web 84 is bent longitudinally to form a wall 88 which, in turn, terminates closely adjacent the web 85 in a longitudinal opening 89, as shown. Web 85 is angularly bent at 90 to terminate closely adjacent the web 86. A longitudinal slotted opening 91 is thereby formed. A flange 92 is secured to the 'web 86 and terminates closely adjacent the outer edge 87 of plate 82 to forma slotted opening 93. The arrangement of webs 84, 85 and 86 is such as to establish longitudinal chambers or passage- Ways 94, 95 and 96, respectively. The air 'which is Y entrapped in each of the chambers or Vpassagevva'ys 94-96 isrelieved of its dust content through'the oriicial openings of slots 89, 91 and 93 during rotation of the rotor. Dust is deposited at the inner surface I12 of the cylindrical housing and passes through slot intoV the collecting and Vdischarge mechanism 49 in the manner previously described. The structure of rotor 79 is such that a'multiplicity of chambers or passageways can be constructed on each plate member'se'cured longitudinally and peripherally of the core structure 80.V Itcan be readily observed that the plate 82 can be lengthened or `shortened to increase or decrease the effective diameter of the' rotor.

The plate 97 may be mounted at each end of rotor 79y In the use and operation of my collector device, dust-k apprese 6 laden air isadmitted tothe pre-swirler 24 andthe blade Z7 causes it to move inwardly toward the rotor and, at the `same time, to pick up rotational velocity. The air then enters the Vanes 67 which are not required lto be pitched and in the form illustrated are flat and unpitched. Vanes 67 rotate at the same rate as rotor 59 or 79. Where these vanes increase in diameter, additional energy is imparted to the air to give it Athe same velocity as it will maintain 4fin' the passageways or chambers within the rotor. yThe air is thus up to its ultimate rotational velocity before it ever enters the chambers or passageways. Since the vanes 67 functionsmoothly and cooperatively (between the preswirlerj and the passageways, no harmful turbulence will be impartedby reason of changing directions or velocities within the longitudinal passageways. Wherethe incoming air contains coarse dust or ygrit particles, the separation may be so fast as to occur at the head end of the collecting and discharge mechanism 49. `Such particles never enter the rotor passageways or chambers but pass directly into the collecting and discharge mechanism. Since the coarse particles of this nature are more apt to cause' Wear 'in the moving parts of the collector,

such wear is restricted to the vanes v67 and that portion of the discharge whichV can be easily repaired or replaced. The remaining dust in the air is separated out through the slotted openings 64 and 66 in the case of rotor 59 and from the slotted openings 89, 91 and 93 in the case of rotor 79. Because of the multiplicity of chambers and the smooth ingress of air from the inlet end, there is a minimum of turbulence and the dust particles are effectively discharged through the slotted openings against the inner wall 12 of the cylindrical housing portion. The dust forms a film which continuously shifts about the inner Wall until .it reaches the lower discharge spot 15 through which it passes into the collecting andl leading to the collector and the resistance in the collector itself. The rest of this negative pressure creates a pressure dierential across the pre-swirler 24 which causes the air to be discharged therefrom tangentally to the rotor at high Velocity. The air now contains velocity energy and, where vanes 67 of increasing diameter are employed, a lesser amount of energy will be required to accelerate the air to the maximum velocity of the horizontalpassageways or chambers. Since the rotor turns at one constant speed and there is a constant volume of air, the only way the velocity of the air can be changed is by increasing ordecreasing the radius'at which it rotates. As the radius is increased, the velocity increases. This takes energy to accelerate the air to the new velocity. Where the radius is decreased, the velocity becomes less and energy is given up. Thus, where the blades or vanes 72 are decreased in diameter prior to the discharged clean yair entering the centrifugal fan housing 75, energy is imparted tothe blades or Vanes 72. In order to convert the greatest amount of energy, it is desirable to bring it to the smallest practical discharge radius before it is discharged into the fan. The air thus contains less residual energy than if it were discharged atr-a larger radins.l There are naturally size limitations to be con data of a collector made according to my invention is as follows:

Dust-laden air enters the collector through a system of ducts that have a frictional resistance of four inches of water at 3600 feet kper minute. The rate of air flow is 3000 cubic Afeet per minute, and the input air temperature is 70 degrees Fahrenheit. The collector rotor is rotated at 3000 r.p.m. The discharge fan has a fteen inch wheel diameter and the blades are curved rearwardly at 75 degrees at their tip. A pressure of 12 inches of water is developed by the fan. The pressure differential across the pre-swirler is approximately 8 inches ofwater since the duct and the collector accelerates the gas across the pre-swirler at approximately 770() feet per minute, taking into account the fact that the pre-swirler is 90% efficient.

The air enters the collector at 3600 feet per minute and is accelerated to 8500 feetper minute through the pre-swirler 24. The air now contains approximately 4.2

horsepower of velocity energy before it enters the rotor 59. The air enters the rotor vanes 67 and is slowed down to 6690 feet per minute at the mean diameter. Thus, the lhigh velocity air has given some of its energy to the rotor 59. As the air proceeds to the passagoways or chambers 62, it is nally accelerated to a velocity of nearly 13,500 feet per minute and it maintains this velocity through the horizontal passageways. Upon leaving the passageways after separation of the dust particles through the discharge slots, the air velocity is slowed downto 660() feet per minute as it enters the fan inlets. The gas leaves the fan with energy equivalent to 5.8 horsepower. The kinetic energy is converted into Vpressure energy by the blades '72, fan housing 75 and diffuser 77, most of which pressure energy is translated through the entire collector to assist in pouring air into the pre-swirler 24. Without the pre-swirler, the power required by the machine is approximately that of the kinetic energy of the air as it leaves the outlet fan which is approximately 7.3 horespower. Without constricting the outlet opening from the rotor to the housing '75, the power requirement becomes roughly 10.5 horsepower. Since the pre-swirler gives the collector rotor 4.2 horsepower of energy and the fan requires 7.3 horsepower, the .net energy which must be supplied to the collector is only 3.1 horsepower compared to the more than 10.5 horsepower which is required without my reclaiming process. There are, of course, other unavoidable frictional losses which occur between the rotor and the stationary housing and such los-ses plus other frictional losses total about 10 horsepower in the instant example. The total horsepower requirement thus becomes 13.1 and it has been found that a horsepower motor may be used in practice to operate the given collector instead of a 25 horsepower motor which is required without the reclaiming` :means set forth.

What I claim is:

1. Apparatus for separating finely divided solids from suspension in a gaseous medium which comprises, a fixed housing having a medial cylindrical body and an inlet portionwith a tangential gas inlet in one end and an outlet portion with a tangential gas outlet at the other end thereof, a rotor coaxially journaled in close clearance ywithin the housing and having elongated smooth-Walled passageways formedgenerallyrparallel to the axis thereof, s'aid rotor having, peripheral-slotted openings communicatingwith each ofsaid passageways, a plurality of vanes secured to said rotor coaxially therewith andlying in close clearance with the inlet end of `said. cylindrical body, a spirally bladed iixed pre-swirler interposed in the inlet portion adjacent said vanes whereby to preliminarily rotate the incoming gaseousY medium and its divided solids suspended therein, and a work reclaiming element having bla es secured lcoaxially with said, rotor within said housing at the outlet end thereof.

.12.Apparatus forseparating finely dividedfsolids from g suspension in a gaseous medium which comprises, a fixed housing having a medial cylindrical body and an inlet portion with a tangential gas inlet in one end and an outlet portion with a tangential gas outlet at the other end thereof, a rotor coaxially journaled in close clearance within the housing and having elongated smooth- `walled passageways formed generally parallel to the axis thereof, said rotor having peripheral slotted openings .communicating with said passageways, a plurality of ilat vanes secured to said rotor coaxially therewith and lying in close clearance with the inlet end of said cylindrical body and increasing in diameter from the inlet to the rotor for-imparting increased centrifugal force upon the gaseous medium and its suspended solids, a spirally bladed pre-swirler fixed with respect to said housing and interposed in the inlet portion outwardly of said flatvanes whereby to preliminarily rotate the incoming gaseous medium and its divided solids suspended therein, anda work reclaiming element having blades secured coaxially with said rotor within said housing at the outlet end thereof, said blades being of decreasing diametercutwardly of the rotor at the outlet end.

3. .ln apparatus for separating dust from air, the corn- -bination of a main rotor housing having a discharge opening therein, an intake fan housing secured to one end of the said main rotor housing and having an axial inlet opening, an intake pre-swirler housing having a tangential opening, pre-swirler means iix'edly mounted in the intake pre-swirler housing adjacent the intake fan housing and communicating axially therewith, an outlet fan housing secured to the other end of said main rotor housing, a shaft journaled through all of said housings, a chambered rotor element mounted on said shaft within said main rotor housing and having elongated passageways substantially parallel to said shaft and having peripheral slotted outlets formed respectively therein, a momentum-conditioning fan secured to said shaft and rotatable in close clearance within said intake fan housing, an energy reclaiming fan secured to said shaft within said outlet fan housing and in close clearance therewith, and

.mechanism communicating with said discharge opening in the main rotor housing for collecting and discharging gas.

4. In apparatus for separating finely divided solids from suspension in a gaseous medium, the combination of a xed housing having a medial cylindrical body and a gas inlet at one end and a gas outlet at the other end, a rotor coaxially journaled in close clearance within said housing and having smooth-walled longitudinal passageways formed in open-ended relation parallel to the axis of said rotor, each of said passageways having a narrow and elongated peripheral slotted opening for discharging dust against the inner wall of said cylindrical body, means coaxially mounted at the inlet end of said cylindrical body for imparting centrifugal force to the gaseous medium and its suspended solids prior to entering said rotor, and means coaxially mounted to said rotor within the outlet end of said housing for reclaiming kinetic energy of said gaseous medium and suspended solids as they pass from the rotor to the gas outlet end of the housing.

5. Apparatus for separating finely divided solids from suspension a gaseous medium which comprises, a fixed housing having a medial cylindrical body and a gas `inlet at one end and a gas outlet at the otherendthereof,

'arotor coaxially journalled in` close clearance within the .housingvand having a plurality of elongated passageways Vin contiguous relation formed generally` parallel. to .the

.of vanes mounted coaxially of said rotor and adjacent 'the inlet ends of said plurality of passageways and adapted to travel at the same angular velocity as said Vrotor whereby to impart centrifugal force upon said gaseous medium and suspended solids therein and to permitthe same to enter said passageways in smooth ilow, -a work reclaiming element having blades coaxially mounted with said rotor and within said housing, and avtangential 'discharge passageway formed in the outlet end -to receive cleaned gas from the housing and to place thegas within r' the housing under reduced. pressure.

6. The-apparatus set forth in claim 5, wherein said tangential discharge passageway has -a flared terminus for converting velocity energy of the discharged gases into pressure energy. v

7. Apparatus for separating nely divided solids from y suspension in a gaseous medium which comprises, a ixed housing having a medial cylindrical body and a gas inlet in one end and a gas outlet at the other end thereof, a

rotor coaxially journaled in close clearance within Athe housing and having elongated smooth-walled pasasgeways formed generally parallel to the axis thereof vand extending completely therethrough, said rotor having peripheral' slotted openings communicating with each of said passage- W-ays, a plurality of radial vanes secured to said rotor coaxially therewith and lying in close clearance with the inlet end of said cylindrical body, an annular plate secured to the inner circumference of said xed housing and lying in spaced relation between the rotor and said vanes, an orice through the housing radially outward of said vanes, and means communicating with said orifice for removal of coarse suspended particles preliminarily l separated by the vanes. l

8. In apparatus for separating `finely dividedsolids fromrsuspension in a gaseous medium, the combination of aV fixed housing having' a-medial cylindrical body andi? a gasV inlet at oneend and a gas outlet at the other end,

-a rotorcoaxially journaledinclose clearancewithin said housing, a plurality of elongated smooth-walled longitu-IA dinal passageways having constant cross section throughvout theirV lengths and lying in open-ended relation within said rotor and parallel to the axis thereof, each of said passageways having -a Vnarrow and velongated slotted peripheral opening for discharging dust against the inner wall of said cylindrical body, and means coaxially mounted at the inlet end of said cylindrical body for imparting centrifugal force to the gaseous medium and rits suspended solids prior to entering said'rotor,

References Cited in the levof this patent UNITED STATES PATENTS 

